From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Turquette Date: Wed, 27 Jun 2012 00:47:10 +0000 Subject: Re: [PATCH 05/11] OMAPDSS: add clk_prepare and clk_unprepare Message-Id: <20120627004709.GA22766@gmail.com> List-Id: References: <1340372890-10091-1-git-send-email-rnayak@ti.com> <1340372890-10091-6-git-send-email-rnayak@ti.com> <1340604478.12683.25.camel@lappyti> <4FE80C43.6090802@ti.com> <1340611133.3395.3.camel@deskari> <4FE85005.4090303@ti.com> <1340630090.3395.85.camel@deskari> In-Reply-To: <1340630090.3395.85.camel@deskari> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On 20120625-16:14, Tomi Valkeinen wrote: > A question about clk_prepare/unprepare, not directly related: let's say > I have a driver for some HW block. The driver doesn't use clk functions, > but uses runtime PM. The driver also sets pm_runtime_irq_safe(). > > Now, the driver can call pm_runtime_get_sync() in an atomic context, and > this would lead to the underlying framework (hwmod, omap_device, I don't > know who =) enabling the func clock for that HW. But this would happen > in atomic context, so the underlying framework can't use clk_prepare. > > How does the underlying framework handle that case? (sorry if that's a > stupid question =). > I think it's a good question! If we're going to call clk_prepare_enable from within a runtime pm callback then I think we'll need to check if _irq_safe() is set and conditionally call only clk_enable in such a case. I'm not a runtime pm expert, but if the driver owns the responsibility of calling pm_runtime_irq_safe then the driver has the proper context to know that it should call clk_prepare BEFORE calling pm_runtime_get_sync. However if some other framework (outside of the driver) calls pm_runtime_irq_safe then it will be difficult for the driver to know what to do... Regards, Mike > Tomi >